Project Summary Recent advances in multiunit recording arrays have revolutionized the field of systems neuroscience. For example, over the past decade the multi-channel arrays fabricated by Multi-Channel Systems have been used by dozens of laboratories to publish hundreds of journal articles, pushing forward our understanding of information processing by large populations of neurons. As useful as well-based multichannel electrode arrays are, existing products do not adequately meet the need for systems capable of accessing the top of slice preparations. High-density transparent electrode arrays that can be accurately positioned on the top of slice preparations can greatly enhance experimental ease and capability. The ability to view underlying structures and reposition the array if necessary can dramatically improve experimental throughput and efficiency. The transparency of the arrays enables the use of optical recording techniques as well as patch-clamp methods in conjunction with multi channel stimulation and recording without having to look through or access structures deep within the slice. This Small Business Innovation Research Phase I project will investigate transparent electrode arrays with small electrode size and pitch, which can be accurately positioned on a slice. The products based on the proposed electrode arrays will enable neurophysiologists to explore neuronal circuitry with stimulation and recording electrode arrays that can be accurately positioned on top of a slice preparation. The goal of this Phase I project is to investigate the feasibility and limits of the manufacturing technology for use in a wide range of electrode array designs. The 32 channel arrays will be microfabricated out of low-stress silicon nitride and metal and will have a minimum electrode diameter of ~4 um distributed over a maximum area of 4 mm2. The electrical and mechanical properties of prototype electrode arrays will be evaluated. The data generated from this Phase I study will be used to develop limits and design rules to be employed by end users in the design customized electrode arrays. Array packaging will be developed in a manner facilitating their eventual wide-spread use by brain-slice research community. PUBLIC HEALTH RELEVANCE The proposed system will enable the large population of researchers that work with brain-slice preparations to compliment their research with high-resolution multi- electrode electrophysiology that can be easily positioned and repositioned. The ability to perform novel electrophysiological experiments by using a catalogue of standard and custom arrays will allow important issues of public health (neural diseases and behavior) to be studied with an unprecedented level of capability. The range of physical scales of the proposed probe array technology is small enough to target tiny regions of the neural tissue, while possessing transparency that allows for the accurate positioning of many electrodes needed to obtain valuable data. [unreadable] [unreadable] [unreadable]